Undesirable phone calls (call, calls) are a common experience for many users. While some calls can be undesirable simply for being annoying, other calls can be undesirable due to their potential to cause harm to persons or property.
For example, a telemarketing phone call is annoying in most cases due to the insistent manner in which the caller seeks to sell something. A call to offer fraudulent sale of securities or real estate can cause serious damage to a person's finances. As another example, a fraudulent call to misinform a user about their credit and commit identity theft has the potential to cause harm to the user's person and property.
Many phone service providers and call-related applications attempt to block undesirable calls using one or more lists of phone numbers. The lists are often referred to as blacklists, and include phone numbers from which undesirable calls are known to originate.
When a user is using a blacklist and receives an undesirable call, a caller identifier (caller ID) identifies the phone number associated with the undesirable call. If the phone number exists in the blacklist, the blacklist prevents the call from ringing the phone, disconnects the undesirable call, sends the undesirable call to voicemail, plays a pre-recorded message to the caller, or some combination thereof.